1. 1
Optimization of a Chem-E-Car
New Jersey Governor’s School of Engineering and Technology 2014
Michael Amoako David Fan Wendy Ide
michael.amoako2015@gmail.com fanjiatian@gmail.com wenfen10@gmail.com
Teaneck High School Montgomery High School High Technology HS
Nina Lin Marcus Loo
missninalin@gmail.com slayer71432@gmail.com
Lenape High School Park Ridge High School
Abstract
In light of the recent movement towards
reducing fossil fuel consumption, the need
for a suitable alternative energy source is
greater than ever. To explore the utility of
household products as unconventional yet
efficient energy sources, a car powered
entirely by chemical reactions was built.
Fuel cell batteries of varying salinity, pH,
and designs were built and tested while a
stopping mechanism was calibrated. A
shoebox-sized car was then built with both
the battery and stopping mechanism
implemented and tested at various distances
and loads. It was found that increasing
salinity increased battery current but did not
affect the voltage, while increasing and
decreasing pH both increased current and
voltage. The iodine clock reaction was also
found to follow a first-order law, with a
reaction time linearly proportional to the
concentration of iodine. Ultimately, the car
was able to stop at each intended distance
through the iodine clock reaction. Although
the aluminum batteries and iodine clock
were implemented to power only a shoebox
sized car, the scale-up of similar, widely
available materials could possibly mean a
future of globally accessible transportation.
.
Introduction
The need for affordable and efficient
alternative energy sources is a defining issue
of the twenty-first century that is receiving
growing attention from both the scientific
community and the public alike. While
hydrocarbons have driven a majority of the
world’s energy consumption for over a
century, such sources are both unsustainable
and environmentally detrimental. If the
world’s energy needs continue to grow at
their current rate, fossil fuel reserves are
estimated to deplete by 2052, followed by
natural gas by 2060 and coal by 2088.1
The
consequences of using these energy sources
to the end will be unprecedented, both for
the environment and the global economy.
Thus, it is clear that the world needs to find
a feasible alternative.
While substantial advances in
alternative energy have recently been made
in the automobile industry, current
alternative energy sources for powering
vehicles are either expensive or not widely
accessible to all. Ethanol fuels, for example,
are not practical because they provide low
mileage per gallon and require a large
amount of organic material and land to
produce, land that is increasingly difficult to
provide.2
Currently, hydrogen fuel cars are
very expensive and often require high
2. 2
running temperatures, reducing their
longevity and efficacy. In addition,
hydrogen fuel is difficult to safely transport
for mass distribution because it needs to be
compressed and purified.2
Because of the
public’s inaccessibility to many “green”
technologies, the future depends on
developing a less demanding way to
encourage the use of alternative energy in
vehicles.
The objective of this project is to
investigate and employ common household
products as nonconventional energy sources
in a car powered entirely by chemical
reactions. The car must also be able to travel
variable distances and carry variable loads
with no additional user input. In addition,
the goal is to gain a better understanding of
how chemical reactions can be calibrated to
automate processes and how engineers
optimize what is available to achieve the
intended goal. The project began by
conceptualizing, building, and optimizing a
battery system and stopping mechanism
before finally building the actual car and
testing it.
2. Background
2.1 Basic Electrochemistry
Electrochemical processes employ both
oxidation and reduction, which are the loss
and gain of electrons, respectively. When
paired together in a redox reaction, electrons
flow from the reducing agent (substance that
is oxidized—loses electrons) to the oxidizing
agent (substance that is reduced—gains
electrons), generating electrical potential
energy that can be harnessed to perform
work, i.e., on a motor.
Galvanic cells can harness this energy
by separating the oxidation and reduction
processes and diverting the electrons
produced through an external circuit.3
The
anode half-cell is the site of oxidation while
the cathode half-cell is the site of reduction,
and both are connected by a salt bridge. The
salt bridge contains an electrolyte or
aqueous solution of ions, which flow freely
between the anode and cathode to maintain
charge neutrality in each. Without the salt
bridge, the cathode would become
progressively more negative as it gains
electrons, while the anode would become
progressively more positive.4
Since
electrons always flow from the substance
being oxidized to the substance being
reduced, this buildup of charge would render
the cell nonfunctional.
Cell potential, the difference in ability
of electrons to flow from one place to
another or the difference between the anode
and cathode potential to become oxidized,
can be quantified in volts (V) as voltage.
Cell potential can also be thought of as the
potential energy that drives redox
reactions.4,5
In this sense, electrons fall from
the anode, which has a higher potential to
become oxidized, to the cathode which has a
lower potential to become oxidized. Cell
potential is calculated by subtracting the
reduction potentials of the anode half-
reaction from that of the cathode half-
reaction (E0
cell = E0
cathode - E0
anode), or adding
the oxidation potential of the anode half-
reaction to the reduction potential of the
cathode half-reaction (E0
cell = E0
anode +
E0
cathode). Oxidation potential is the negative
of reduction potential since both are
opposite processes.
2.2 Circuits
Circuit configuration is essential to
maximizing voltage and current output as
differently designed circuits have various
electrical properties. Series circuits allow
electrons to flow in only one direction, while
parallel circuits allow electrons to flow in
multiple directions.6
Electron flow is
severed when one component of a series
circuit fails. Because the car photoreceptor,
3. 3
motor, and power source are wired in series,
the circuit is broken when the photoreceptor
no longer receives light (see Diagram 1).
However, in a parallel circuit, if one
component fails, the rest of the components
still receive electron flow.7
Three definitions that require an
understanding of basic circuitry are as
follow:
1. Voltage (V) is the measure of
potential difference between two points, in
volts (V)
2. Current (I) accounts for the amount
of electrons that flow in the wire, in amperes
(A)
3. Resistance (R) measures any
hindrance of movement for the electrons, in
ohms (Ω)
Mathematically, voltage, current, and
resistance are related by Ohm’s Law: V =
IR.5
Power (Watts) is defined as P = IV for
ohmic circuits.
In a series circuit, the total resistance
equals the sum of the individual resistances
of the components. Current is uniform
throughout a series circuit and voltage drops
split proportionally. Note that since current
(I) is constant through a series circuit for
resistors, V and R are directly proportional.
Therefore, higher resistors experience
greater voltage drops than lower resistors.
In a parallel circuit, total resistance is
the reciprocal of the sum of the reciprocals
of each individual resistance. When wired in
parallel, the components experience
equivalent voltage drops and split current
proportionally. Since voltage is constant
over resistors in parallel, I and R are
inversely proportional to each other. This
means that higher resistors let less current
pass through them than lower resistors when
in parallel.
When batteries are wired in series, their
voltages add. On the other hand, when
batteries are wired in parallel, the total
voltage equals the voltage of a single cell.
The advantage to wiring batteries in parallel
is that the overall current capacity increases.
In order to generate enough current to power
the car, three different wiring methods can
be followed—series, parallel or a hybrid
configuration.
2.3 Aluminum-Air Batteries
Aluminum and oxygen act as the
anode and cathode, respectively, in the car.
While oxygen itself is reduced in the battery,
activated carbon is used as an adsorbent to
capture oxygen upon contact with the air.
Because activated carbon is very porous, its
large surface area allows it to capture
oxygen on its surface, facilitating the
reaction of oxygen with water to form
hydroxide ion, which then reacts with
aluminum itself. Paper towels drenched in
saline solution serve as the salt-bridge that
preserves charge neutrality in each half-cell,
while copper wires transfer electron flow to
the DC motor.
The consistency of carbon directly
affects oxygen’s rate of diffusion through
the salt solution and into the aluminum
anode. According to Fick’s Law, the rate of
diffusion is directly proportional to surface
area and concentration difference, but
inversely proportional to the distance over
which diffusion occurs.7
The size of the
activated carbon particles gives perspective
Diagram 1
4. 4
into the manner in which mass transport
occurs in a reaction chamber. In this case,
oxygen from the air diffuses into the porous
medium with the help of activated carbon.
The surface of the carbon between particles
act as a ‘oxygen carrier’ and eventually
initiates the reduction process with the
electrolyte solution. Larger particles will not
be able to carry out the adsorption process
due to their limited surface area, while
smaller particles will impede the diffusion of
oxygen. Therefore, coarse, fine, and semi-
coarse consistencies were tested.
The following half-reactions take
place in the aluminum-air batteries, as
shown in Equation 1 and 2. The standard
cell potential of the cell is calculated using
Equation three. 6
(1) Cathode: O2(g) + 2H2O(l) + 4e-
→ 4OH-
Eo
= + 0.40
(2) Anode: Al(s) + 3OH-
(aq) →
Al(OH)3(s) + 3e-
Eo
= - 2.31
(3) Overall reaction: 4Al + 3O2 + 6H2O →
4Al(OH)3 Eo
net = 2.71
When vinegar is added to the cell,
cell potential is expected to increase because
of specific chemical changes. Normally
aluminum reacts with OH- to create
aluminum oxide, however by adding vinegar
(5% acetic acid), the dissociated H+
ions
react with oxygen to form water and prevent
aluminum from coming in contact with
oxygen. But since the aluminum comes in
contact with water, it is oxidized into
aluminum ion, Al+3
. This results in a higher
cell potential.
Overall reaction: Al + 3H+
+ ¾O2 →
Al3+
+ ³/₂ H2O Eo
net = 2.91
When bleach is added to the cell, the
cell potential is higher because HOCl, which
has a higher reduction potential, is reduced
instead of oxygen. Thus, both increasing and
decreasing pH are hypothesized to increase
cell voltage and current.8
This can be seen in
Equations 4 and 5.
(4) ClO- + H2O + 2e-
→ Cl-
+ 2OH-
Eo
net = 0.89
(5) HOCl + H+
+ e-
→ ½Cl2 (g) + H2O
Eo
net = 1.63
By adding Aluminum to this, two more
possible reactions can take place, in
equations 6 and 7.
(6) 3OCl-
+ 2Al + 2OH-
+ H2O → 3Cl-
+
2Al(OH)4
-
Eo
net = 3.21
(7) HOCl + Al → Al(OH)3(s) + ³/₂ Cl2 (g)
Eo
net = 3.93
2.4 Iodine Clock Reaction
The iodine clock reaction is a classic
example of a chemical clock; a mixture of
reactants in which sudden property changes
occur when concentration rises past a certain
threshold.8
Clock reactions are often used by
educators to help students visualize reaction
kinetics, as changes in temperature and
concentration (and thus reaction rate) are
directly seen as color change.
Because this project utilized only
household products, the iodine clock used in
the car differed slightly from the traditional
clock reaction which uses ACS grade
chemicals. This variant involves two main
solutions. The first solution is composed of
Vitamin C and iodine while the second
solution is composed of hydrogen peroxide
and starch. Vitamin C and iodine undergo a
redox reaction in which Vitamin C acts an
electron donor, preventing the iodine from
forming a complex with starch. Once all the
Vitamin C reacts, the iodine is then free to
form a complex with starch, which induces
5. 5
the solution to change from clear to dark-
blue. Because iodine is the limiting reactant
that dictates when color change is induced,
iodine concentration can be manipulated to
change the reaction rate. All solutions were
kept at room temperature to ensure
consistency between results. The two
simultaneous reactions involved in the
iodine clock are shown below in equations 5
and 6.
2H+
(aq) + 2I-
(aq) H2O2(aq) → I2(aq) +
2H2O(l)
I2(aq) + C6H8O6(aq) → 2H+
(aq) + 2I-
(aq) +
C6H6O6(aq)
where: I-
= iodide ion
H2O2 = Hydrogen peroxide
I2(aq) or I3
-
= Iodine (aq.) or
triiodide ion
C6H8O6 = Ascorbic acid
C6H6O6 = Dehydroascorbic
acid
2.5 Role of Iodine Clock in Stopping
Mechanism
The car circuit contains a motor,
photoreceptor and batteries. When the car
first starts, a flashlight shines through a glass
beaker containing the iodine clock onto the
photoreceptor, switching it “on” and keeping
the circuit closed. At this point, the beaker is
clear as the iodine clock reaction has not
reached completion. As the iodine clock
reaction progresses, the car continues to
move until the glass beaker suddenly turns
dark, preventing light from reaching the
photoreceptor and breaking the circuit.
Because reaction time is a function of iodine
concentration and can be easily measured,
the iodine clock can be effectively calibrated
to control the time and distance that the car
travels for.
See Diagram 2 on page 14.
3. Implementing the Car Design
3.1 Starting Mechanism
All batteries were made using cheap
and easily accessible household products.
While parameters such as battery dimension,
carbon mass and consistency, and circuitry
were modified between design iterations, the
following describes the final “CD case
design” that proved to be the most
successful.
Each CD case contained four cells
which were made simultaneously. See
Figures 1 and 2 for schematics of one cell.
Two 9-10 cm long pieces of copper wire
were then cut with one being taped onto the
CD case (-).
Next, a 11 x11 cm piece of aluminum
foil and paper towel were cut out and each
folded into 5.5 x 11 cm pieces, and placed
on top of the first copper wire (-). The
folded paper towel was then soaked with 5
ml of salt water solution (concentration
varied by trial) and placed on top of the
aluminum foil again.
The second copper wire (+) was placed
on the wetted paper towel and covered with
the pre-prepared carbon. The carbon was
only spread on either the right or left half of
the paper towel, leaving the other side blank.
Depending on whether pH was manipulated,
2 ml of vinegar or bleach were then
sprinkled on top of the carbon to decrease
and increase pH respectively. Finally, the
entire cell was folded in half to 5.5 x 5.5 cm
and secured in the CD case with binder
clips.
After each cell’s voltage and current
was measured, the cells were then wired in
varied combinations of series and parallel
circuits to maximize voltage and current
respectively. The cells were connected in
series by connecting the positive wires
(inside paper towel and graphite) to the
6. 6
negative wires (touching aluminum foil).
The cells were connected in parallel by
connecting positive to positive and negative
to negative wires (see Figures 3 and 4).
It was important to ensure that the
crushed carbon was uniformly moist
because the salt solution proactively
balances charge.9
Whenever the crushed
carbon dried out, the cell had to be wetted in
order to sustain voltage production. It was
also important to ensure that the copper
wires spanned the width of the battery so
that surface area for conducting electron
flow was maximized.
Previous designs were similar to the one
described above, but used plastic sheets and
clamps instead of binder clips, making them
much heavier and impractical for
implementation in the car.
Table 1. Material costs for Aluminum-
Air Battery
PRODUCT COST
Heavy Duty Aluminum Foil $5.08
Copper Wires (18 gauge, x5) $16.20
Slim CD and DVD Storage Cases
(50/pk.)
$11.54
White Vinegar Distilled $8.99
Clorox Bleach $7.28
Morton Iodized Salt (x2) $5.44
Figure 1
(side view diagram of open cell)
Figure 2
(layered diagram of folded cell)
Figure 3
(CD case of four cells in series)
Figure 4
(CD case of four cells in parallel)
7. 7
Bounty Paper Towels $5.97
ACCO Binder Clips $4.36
NSI PVC Tape $2.15
Black Diamond Premium Activated
Carbon
$13.59
TOTAL (incl. taxes): $86.24
3.2 Stopping Mechanism
A well-mixed solution of extremely fine
crushed Vitamin C tablet and 60 ml of warm
water was first prepared. 5 ml of this
solution was then transferred to a second
beaker (labeled Beaker B) containing 60 ml
of warm water and 4-6 ml of iodine
(increments of 0.1 ml were tested in each
successive trial). The solution turned clear
upon adding the Vitamin C and was also
allowed to cool to room temperature.
Finally, 60 ml of warm water, 15 ml of
hydrogen-peroxide and 2.5 ml of liquid
starch were added to a third beaker (labeled
Beaker C), well stirred and allowed to cool
to room temperature. Beaker B was added to
Beaker C and the time required for color
change was recorded. Trials were conducted
in this fashion for varied amounts of iodine
in order to observe the resultant changes in
reaction rate.8
Table 2. Material costs for Stopping
Mechanism
PRODUCT COST
Hydrogen Peroxide (3%) $5.30
Rite Aid Antiseptic Solution (x2) $23.98
Sta-Flo Liquid Starch $7.00
Ester-C Vitamin C tablets $10.08
Total (incl. taxes): $49.61
3.3 Building the Car and Performing
the Load Tests
A 30 x 23 x 0.50 cm plexiglass car base
containing four 5.0 cm radius wheels from a
previous Rutgers AIChe car was removed
and modified for our car. A 1.5 V, 7600
RPM motor was first wired in series to the
battery setup. A photoreceptor switch was
then wired to the battery and placed inside a
covered cardboard roll. Next, a hole was cut
in the cardboard and a flashlight was
inserted and allowed to shine inside the roll.
Finally, an empty beaker for the iodine clock
reaction was placed in between the
photoreceptor switch and the flashlight.
Load tests were performed to analyze
the car’s performance while traveling at
various distances, voltages and loads. Loads
of up to 500 ml of water were tested in 50
ml increments for 3, 4.5 and 6 V batteries.
At the start of each trial, the pre-prepared
iodine clock solutions were added to the
empty beaker and the cardboard container
was covered to block out light. The amount
of time required to travel 10 feet was
recorded for each variation in load and
voltage. Upon conducting these trials,
average velocity were calculated using
kinematic equations. Acceleration was not
taken into consideration as the car traveled
at a constant speed and came to an abrupt
stop after the stopping mechanism had taken
place. The velocity at each load and voltage
was then used to predict the amount of time
it would to take to travel at 20, 30, 40 and 50
feet with those same parameters. Because
acceleration was negligible, these
calculations are representative of the car’s
motion at those distances.
Table 3. Material costs for Modeled
Car
PRODUCT COST
Acrylic Plexiglass Sheet (x2) $17.94
8. 8
Morphibians Rover $21.99
Energizer 9V Alkaline Battery (x2) $7.65
Mini Cree LED Flashlight $2.45
Duracell AA Battery $4.39
Total (incl. taxes): $58.23
4. Results and Discussion
4.1 Aluminum-Air Batteries
4.1.1 Individual Cell vs. Battery
Voltages
When the original 7 cm x 12 cm paper
towel, unfolded, and 5% saltwater cells were
tested, each yielded an average voltage of
0.6-0.8 V and current of 0.01 A. Multiple
plastic sheets and metal clamps were used to
bind the cells together in a series battery;
however, this setup was excessively heavy
and difficult to work with. The aluminum
rusted easily and saltwater often leaked out,
drying out the cells prematurely. Due to
these difficulties, it was decided to
implement the aforementioned CD case
design, the design in which each case or
battery contained four 5.5 cm x 5.5 cm
folded cells. Surprisingly, batteries built to
these specs also yielded 0.6-0.8 V despite
being much smaller in surface area. This can
be attributed to cell potential’s intensive
property, which makes cell potential
independent of the number of electrons
transferred or amount of material present.1
Consistently, adding more carbon did not
change the amount of voltage produced
either, since the density of carbon remained
the same; 5.5 cm x 5.5 cm cells with 1.5 g,
2.0 g and 2.5 g of carbon respectively also
yielded 0.6-0.8 V. However cells with more
carbon seemed to maintain their voltage
longer, probably because more reactants
were available to react, thus lengthening the
duration of reaction. Because each CD case
battery could easily hold four cells while
being significantly lighter and more durable
than the plastic clamp design, the CD case
design was implemented into the car.
Although each four-cell battery alone
produced about 2.2 V on average, the total
voltage produced by wiring multiple cells
together in series was significantly lower
than expected. Three separate series-circuits
each composed of four batteries (16 cells)
were built, and each circuit averaged only 5
V - about 56.8% of the expected 8.8 V yield.
This voltage drop could be due to the
lengthy period of time spent wiring the
batteries together. During this time, oxygen
levels likely plummeted while aluminum
hydroxide (non-electrically conductive)
likely accumulated on the aluminum foil as
a byproduct of redox reactions, which would
reduce the amount of oxygen available to
react and also increase resistance, thus
reducing voltage. Despite the significant loss
in voltage, each circuit should have been
able to run the motor because one
commercial AA battery (1.5 V total)
sufficed previously, however, none of the
three circuits succeeded. This was due to the
circuits’ low current of 0.01 A, which is
significantly less than the commercial
batteries’ combined current of around 3 A.
Because the previous three circuits were
wired in series, each had the combined
voltages of all cells involved but the current
of only one cell. Thus to increase current,
cells were wired in a series/parallel hybrid
configuration instead. Four batteries were
wired in series, and four of these series
packs were wired in parallel. This setup
produced around 2 V and 0.18 A, but still
failed to power the motor. Because each
individual cell contained only 0.01 A, it was
not surprising that the series/parallel setup
did not experience a significant enough
increase in current. When making the cells,
the pH and salinity were manipulated in
order to try to maximize current and voltage.
9. 9
The data collected from changing either the
pH or salinity of the cells were compared
with each other." See Figures 5 and 6.
4.1.2 Effect of Salinity on Voltage and
Current
The previously mentioned battery cells
were all made with 5% salt solution.
Because saltwater served as the ion bridge
for the battery, it was hypothesized that an
increase in salinity would increase voltage
and current due to the battery’s larger
capacity for neutralizing charge in the anode
and cathode. Interestingly, raising the
salinity to 10%, 12%, 15% and 20% by mass
respectively did not significantly impact
voltage. While 12% salt solution exhibited
slightly higher average voltages than 5% and
15%, both 10% and 20% were higher than
12%. In addition, voltage difference
between the five concentrations never
exceeded 0.07 V, which is an unexpectedly
marginal difference for such large
differences in salt content. Any differences
in voltage were likely due to minor
variations between cells or limitations in
device accuracy. However as expected,
raising salinity did increase current, with
20% salinity exhibiting the highest average
starting current of 0.22 A for a single cell.
12% salinity has been cited as having the
highest electrical conductance6
; however,
the data collected suggests maximum
conductivity at 20% for pure salt solutions.
When four cells with 20% salt solution
were wired together in series and three in
parallel, the circuit yielded 5 V total (each
cell produced on average 2.2 V and 0.2 A)
and 0.25 A. Again there was a significant
drop in voltage and current, likely for the
same reasons mentioned above. 0.25 A was
still not enough current to run the car, so pH
was next tested.
4.1.3 Effect of pH on Voltage and
Current
It was previously hypothesized by the
group that both an increase and decrease in
pH would increase voltage and current
output, with higher pH experiencing greater
increases due to the bleach reactions’ higher
cell potential of 3.93 V. As expected,
increasing pH through adding bleach did
increase the cell voltage; by 0.045 V on
average. Decreasing pH through adding
vinegar increased the average cell voltage by
0.092 V on average. This was surprising as
the bleach reaction’s cell potential is much
higher than that of the vinegar reaction, and
thus adding bleach should have resulted in
significantly higher average voltages.
Interestingly, vinegar cells were more stable
on average while bleach cells experienced
sharper drops in voltage. Because the
vinegar cell wires remained shiny instead of
turning red, the acetate in vinegar could
have prevented copper oxide from
accumulating on the copper wires, thus
reducing resistance and maintaining contact
with the solution.
Both increasing and decreasing pH
resulted in higher starting currents, with
bleach exhibiting the highest average
starting current for most salt concentrations.
Because of the discrepancy between bleach
and vinegar’s performance in voltage output
and current respectively, other factors such
as electrolyte solubility might affect the
voltage.
When four 20% saltwater w/ bleach
cells were wired in series with three in
parallel, a maximum of 6.7 V and 0.4 A was
produced, although each cell had an average
voltage of 0.8 V and current of 0.25 A. 0.4
A still was not sufficient to run the motor,
and ultimately, no battery configuration
succeeded at doing so. Because of this,
commercial AA batteries were used in the
load tests instead of the aluminum foil
batteries.
10. 10
4.1.4 Proposed Solutions to Challenges
and Additional Findings
Ideally, the car batteries should have
produced higher voltages and currents than
what was observed. As mentioned above,
when cells were wired in series and parallel,
the total voltage and current output dropped
sharply, at times to only 50% of the
expected starting output. This is probably a
limitation incurred by the use of only
household products, which contain many
impurities and only a small percentage of
the active ingredient. If pure ingredients
were to be used, perhaps the batteries would
produce more voltage and current. The
prolonged period of time spent wiring the
cells together also contributed to decreased
voltage and current output. Because it was
difficult to maintain wire contact with the
wet graphite, at times individual cells short
circuited and had to be fixed individually,
which was difficult as the CD case could not
be reopened without unwiring neighboring
cells. The process of opening the CD cases
at times inadvertently damaged previously
functional cells, creating additional
problems. Thus the inaccessibility of
individual cells was a major flaw of the CD
case design that unnecessarily prolonged the
wiring period. Additionally, there were a
limited number of functional multimeters
available in the lab, which impeded the rate
at which batteries could be tested.
The use of alligator clips to connect the
wires is one improvement that could be
implemented. This would potentially
increase accessibility to each cell and tighten
wire contact, decreasing possibilities for
failure. Another improvement could be to
use larger CD cases, increasing the amount
of oxygen available to react and thus
lengthening the runtime of each cell.
Towards the end of the program,
aluminum reactor shape was experimented
in an attempt to further optimize current
output, however, these trials were never
completed. Yet the trials conducted indicate
that modifications in shape are highly
promising in optimizing battery
performance. The most promising shape
tested was that of a log. The log shaped cells
were largely the same as the previous
rectangular cells, except the aluminum foil
was wrapped around a paper towel roll
instead of a flat surface. Each of these cells
produced a surprisingly high average current
of 0.80 A but ordinary voltage of 0.722 V.
This is a significant gain in current, as a
single log cell yielded more current that
almost four rectangular battery cases wired
in parallel. Although the ten log cells
produced were not wired into a circuit, the
individual cell values indicate that a high
current would have been obtained. These
preliminary results are highly promising
with regards to producing high current
aluminum air cells from household products.
Future investigation into this design is
highly suggested.
4.2 Iodine Clock
(see Figure 7)
When iodine was added in 0.1 ml
increments from 4 to 6 ml, the reaction time
was found to follow a linear relationship
with a coefficient of determination (r2
) of
0.93. This linear relationship is expected, as
iodine is the rate determining step and the
rate law is cited in references as being first
order. 11
At first, the group did not obtain a
strictly linear relationship because the
solutions were not all cooled to the same
temperature, and thus all subsequent trials
were conducted at room temperature. At
times Vitamin C fell out of solution, causing
variations in reaction rate. Thus the Vitamin
C had to be remixed prior to each trial.
4.3 Load Tests
(see Figures 8-14)
11. 11
When tests were performed with
various voltages (3, 4.5 and 6 V) and loads
up to 500 ml of water over a distance of 10
feet, it was found that load did not
significantly impact runtime. At higher
voltages, load had an even lesser impact on
the car’s runtime, as indicated by the best fit
line’s smaller slope. All three graphs
showed a near-linear relationship between
load and time, indicating that acceleration
and friction were both negligible. This linear
relationship is further corroborated by r2
values that were all greater than 90%. The
time required to travel 10 feet at each load
and voltage were used to calculate the time
required to travel at 20, 30, 40 and 50 feet.
4.4 Design Economics/Cost Analysis
4.4.1 Battery
The components of the starting
mechanism cost a total of $86.24. While the
starting mechanism was affordable, the
aluminum airfoil battery lacked longevity
and overall performance meaning it would
have to be replaced frequently. The battery
maintained its voltage above 80% (the
standard shelf life mark) for only 10 minutes
at most; barely enough time to run a series
of load tests. Commercial-scale energy
sources require much longer run times.
Furthermore, the aluminum battery’s
inconsistency is a drawback to its
affordability. If better materials had been
used, perhaps a more consistent voltage
could have been obtained, however, cost
might have increased as well. The balance
between cost and quality is delicate.
4.4.2 Stopping Mechanism
Like the starting mechanism, the
components of the stopping mechanism
were relatively cheap. With a total cost of
only $36.78, the stopping mechanism was
not only cost-effective, but efficient. By
controlling the temperature in the reaction,
the group successfully attained both
consistent and reproducible results.
Evidently, the Iodine clock reaction is
practical in that it is affordable, reliable, and
easily prepared. The intended goal for the
stopping mechanism was achieved in the
clock reaction’s ability to stop the car at its
intended distance. In this case, household
chemicals provided to be a viable alternative
to pure ACS grade chemicals.
4.4.3 Car Platform and Components
Similar to the starting and stopping
mechanism, the car platform was fairly
inexpensive. The total cost was $58.23,
again less than the 2012 GSET team’s
$110.10. It should be noted however that the
car base and photoreceptor for this year’s
car were already provided by the project
mentors, which reduced this year’s costs.
4.4.4 Overall Cost
Because a primary goal of the project
was to design a cost-effective, working car
using readily accessible materials, achieving
a suitable price was paramount to
maintaining design feasibility. The project
mentors designated a desired cost of
between $400 and $600, however the end
cost of $194.08 was much lower, making the
car very cheap in comparison. Despite this
low cost, the aforementioned performance
flaws detracted from the car’s price
advantage. Because household products
were used instead of pure chemicals, the
aluminum batteries did not sustain their
expected voltage and current, even though
the iodine clock reaction was successful
with household products. The group saved
money by reusing a previous group’s car
base, however the base was heavy and
difficult to move, which further increased
the base current needed to power the car. In
all, the car was somewhat cost-efficient in
that it was able to achieve the project
12. 12
objectives despite possessing several
drawbacks.
5. Conclusion
When four 20% saltwater and bleach
aluminum-air batteries were wired in series,
the maximum voltage obtained was 6.7 V
with insignificant current. When four cells
were wired in series, and four of these series
packs were wired in parallel, around 2.0
Volts were produced with 0.18 Amps of
current. None of these configurations could
produce enough current to run the motor,
despite having a high enough voltage. Even
four batteries in just parallel could only
produce 0.30 Amps at most.
It was found that increasing salinity
increased current but left voltage unaffected,
while both increasing and decreasing pH
increased current and voltage, with lower
pH experiencing the greatest increases. The
iodine clock reaction was successfully
calibrated to the nearest 0.1 ml and
implemented into the car stopping
mechanism. Reaction time was found to be
linearly dependent on iodine amount with a
high coefficient of determination of 93%,
corroborating its first order rate law and
indicating consistent data values. Although
none of the battery configurations succeeded
in running the car, load tests were performed
with AA batteries containing the same
voltage as our batteries, thus accurately
reflecting our car’s kinematic properties.
5.1 Future Work
The research presented in this project
has raised some questions that can be
answered by future studies in this area.
Firstly, using half-reactions with higher
stability and reduction potential might
provide more voltage and current to power
the car, reducing the number of batteries
needed and potentially improving car speed.
Hydrogen fuel cells are used regularly to
power AIChE cars and would be a viable
option to use for similar Chem-E-Car
projects. In addition, studies should be done
on battery longevity; as mentioned in the
cost analysis, the batteries in this project did
not maintain their voltage for very long.
Because there is a strong need for batteries
with longer shelf life, these research
findings would be beneficial for both
manufacturers and consumers. Besides
finding alternatives that maintain high
voltage, a possible line of research would be
testing the current versus time. Since voltage
is not the only factor needed to keep the car
moving, it is important that in the future,
current could be taken into account of as
well. The car itself could also be improved
upon and even rebuilt as it was heavy and
difficult to move. Finally, perhaps
alternative chemicals such as sodium
thiosulfate and hydrogen chloride could be
investigated for use in the stopping
mechanism instead of iodine, for their
potential accuracy and ease of
implementation.
Though the objective of this research
was to design a shoe sized car, it is possible
that in the future, a vehicle can possibly be
powered entirely by chemical reactions.
Cars today cost an average of $20,000.
Though this car is smaller, the cost was only
$194.08 and much of the costs attributed to
the actual chemicals themselves. Also, since
the products used were household products,
a greater production of either the starting or
stopping mechanism to complement a bigger
car would not be detrimental as these
products are readily accessible to the
consumers.
Acknowledgments
First and foremost, we would like to
thank Dean Jean Patrick Antoine and Dean
Ilene Rosen for granting us an amazing
opportunity to gain firsthand experience in
13. 13
engineering and for organizing an amazing
Governor’s Shool Program that pushed us to
expand and challenge our critical thinking
skills. We give our gratitude to our RTA,
Laura Gunderson, for her patience and
continuous guidance. We would also like to
thank our mentors Joanne Horng, Nicholas
Ngai, Ingrid J. Paredes, Shriram Sundarraj,
Christian Tabedzki, and Mercedes Wu for
dedicating their free time to supervise and
guide us in the lab. We’d especially like to
thank Shriram Sundarraj who dedicated
numerous weekends and worked
unremittingly to help us gain a deep
understanding of our project and finish on
time. We’d also like to thank Morgan
Stanley, Lockheed Martin, Silverline
Windows, Jersey South Industries Inc., the
Provident Bank Foundation, and Novo
Nordisk for sponsoring the program. Lastly
but most importantly, we would like to
thank Rutgers University the Governor
School faculty, and the State of New Jersey
for funding and granting us this unparalleled
opportunity to learn at such a prestigious
program.
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Diagram 2
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Picture 1: Side view of car with load
15. 15
Figure 5 : Voltage drop per cell for different salinity and pH levels.
Figure 6: Current as function of salinity and pH concentration changes
